I did a DIY unit with a few parts from ebay
Pump $12.98
http://www.ebay.com.au/it...mp;hash=item51c9eefd9c Relay $2.19
http://www.ebay.com.au/sc...RM+PIC+AVR&_sop=15 Arduino $3.88
http://www.ebay.com.au/it...mp;hash=item3f37dffa10 Clock $1.22
http://www.ebay.com.au/it...mp;hash=item3f3a685c2e Some parts I had laying around (Power packs and wire).
I then have a small sketch to run the pumps as needed based on time from the clock.
I use two feeds per rotifer bucket so that if I have a failure, on one, they still get a feed.
Overall for 4 rotifer buckets the cost was
Pump $12.98 * 8
Relay $2.19 * 4
Arduino $3.88 * 2 (I also added an LCD and buttons to manually feed, but this was me being fancy).
Clock $1.22 * 2
Power packs, cables, solder etc $20
Total $142.80 for eight pumps plus some time, so an average per pump $17.85.
Each Arduino is attached to four pumps, one to each rotifer bucket.
Each bucket has two feed pumps
I can expand with up to 14 pumps per arduino from memory without having to change the hardware much.
I used two pumps as I was making it all and wanted to ensure it was as reliable as possible.
As it happens, none have failed so far and they have been running for about 3 months now.
I probably could have used 1/2 the equipment.
Total cost for just 1 pump
Pump $12.98,
Relay $2.19, Arduino $3.88, Clock $1.22, Power pack and cables $10 Total $30.27
The entire lot sits inside a fridge. The pumps are attached to a piece of acrylic that they sit on, then feed from containers of algae stored in the fridge (again 2 containers).
regards
Darren